Various types of medical devices include a needle for insertion into the skin of a patient. Such needles are inserted into the skin to serve various diagnostic or therapeutic purposes. For example, a traditional injection syringe is provided with a needle for facilitating a passageway into the patient for injecting fluid into, or withdrawing fluid from, the patient. A traditional phlebotomy apparatus is provided with a needle for withdrawing fluid from a patient and transmitting the withdrawn fluid into an evacuated receptacle. A catheter stylet is provided with a needle for piercing the skin and supporting a catheter cannula on the stylet while the cannula is guided into a desired position within the patient. Each of the aforementioned needle-bearing medical devices can cause transmission of various pathogens, most notably the Human Immune Virus (HIV), due to an accidental needle stick of an uninfected person after the needle is withdrawn from the patient.
It would be desirable to provide a needle retraction mechanism for permanently and reliably retracting a used or contaminated needle into the needle-bearing medical device in order to render the medical device in a safe condition after use. It would further be desirable to provide such a mechanism in a configuration that does not interfere with the customary uses of needle-bearing medical devices, is resistant to undesired activation by forces normally encountered in the use of such medical devices, and can be easily operated without a significant change in the techniques employed by the medical professionals who use needle-bearing medical devices.